i BYZANTINE ARCHITECTURE 33 No school has ever expressed its structure more simply, or given fuller scope to the artist, whether architect or painter. Byzantine architecture is not only a school of construction, it is also a school of painting. Most of the churches of Constantinople have unfortunately lost the latter part of their personality. They are mere ghosts, their skeletons wrapped in a shroud of whitewash. Still the Greek artist retained his skill to the last, and the decorative work of S. Saviour in the Chora will stand comparison even with the similar work in S. Sophia. In Byzantine times the greatness of S. Sophia tended to crush competition. No other ecclesiastical building approached the c Great Church.' But structural ability was only latent, and displayed its old power again in the erection of the imperial mosques of the early Turkish Sultans, for they too are monuments of Greek architectural genius. The origins of Byzantine architecture have been discussed at great length by Strzygowski, Rivoira, and many other able writers. Much work still remains to be done in the investigation of the later Roman and early Byzantine work ; nor does it seem probable that the difficult questions of the Eastern or the Western origin of Byzantine art will ever be finally settled. The beginnings of Byzantine architecture have never been satisfactorily accounted for. With S. Sophia it springs almost at once into full glory; after S. Sophia comes the long decline. It may, however, be noted that the c endings' of Roman architecture are similarly obscure. Such buildings as the Colosseum, in which the order is applied to an arched building, are evidently transitional, the Roman construction and the Greek decoration, though joined, not being merged into one perfect style. Even in the baths and other great buildings of Imperial Rome the decoration is still Greek in form and not yet fully adapted to the arched construction. At Spalatro, in such parts as the Porta Aurea, a developed style seems to be on the point of emerging, but it is not too much to say that in no great Roman building do we find a perfect and homogeneous style.